The secure exchange of computer documents over a network has long been a requirement in many business environments. The most common method employed is to encrypt the document on the sending computer system, and decrypt it on the receiving computer system. An encryption technique that is widely used is based on an asymmetric public/private key pair technique. In public/private key pair encryption, a private key is created, and a public key is generated from the private key using a mathematical algorithm that is practically impossible to apply in reverse. The holder of the private key makes the public key available to all who wish to send encrypted messages to the private key holder. Messages that are encrypted using the public key can only be decrypted by the private key. In this system, security depends on the secrecy of the private key.
Another method that is used for the secure exchange of computer documents employs location-based security. In these methods, access to a document typically depends on the geographic location of the computer systems receiving and/or sending the document. Determining a computer system's geographic location can be done, for example, using a satellite navigation chipset embedded in the computer system that processes signals from one of the satellite navigation systems, such as the Global Positioning System (GPS) maintained by the U.S. Department of Defense. These systems typically will allow access to a document only if the sending and/or receiving systems were or are at particular geographic locations when the document was transmitted by the transmitting system, or opened by the receiving system. Location-based security methods can be used in conjunction with, or integrated into, encryption systems.